Microphone arrays are used in a wide variety of situations for many acoustic applications, including passive-sonar localization, spatial-audio recording, isolation of a desired signal from noise and reverberation, and locating sound sources. For example, acoustic source localization based on microphone array signal processing can be used to locate gunfire or aircraft in defense and homeland-security applications, to localize noise sources in the design and manufacturing process of machines, to identify a speaker in room of people, or to localize an unknown number of spatially distributed sound sources in spatially distributed noise.
All such applications generally require microphone array designs and beamforming techniques that can produce narrow beams to help identify an angular direction of a sound source. In general, accuracy of source localization and array gain improve by increasing the number of array elements. Thus, while there are numerous proposed approaches with respect to sound localization, most require an extremely large number of microphones in the array to collect the necessary acoustic information to localize sound sources. This leads to high implementation costs and significant computational requirements. Accordingly, a need exists for microphone array designs that can provide highly focused beams with a minimum number of microphones in the array.